Conventionally, it is known that a hydraulic pump, driven by an electric motor, and a hydraulic motor, outputting torque by receiving pressurized oil from the hydraulic pump, can be provided integrally with the electric motor (for example, Japanese Patent Application Publication (B1) 53-37523). According to the Japanese Patent Application Publication (B1) 53-37523, the hydraulic variable speed electric motor is provided with a rotor, which is located inwardly of the stator of the electric motor, and a hollow shaft, which is located inwardly of the rotor and which is hollow with both ends being supported by bearings. The hollow shaft is electrically driven integrally with the rotor, and is used as an input shaft for the power of the hydraulic pump. A projecting shaft, which is integral with the outside case for the stator and rotor of the electric motor is fixedly provided at the hollow shaft. The hydraulic pump is provided in the direction of the outer diameter of the projecting shaft and axially adjacent to the stator and the rotor of the electric motor. The hollow shaft and the projecting shaft, provided fixedly and integrally with the hollow shaft, are supported by the bearings at three points. The hydraulic motor is provided inside the hollow shaft so as to oppose the hydraulic pump. The pressurized oil from the hydraulic pump goes to the external case of the electric motor, from the hydraulic pump through the rotating hollow shaft and the integrated projecting shaft and is further sent from the external case to the hydraulic motor.
However, in the above-described conventional hydraulic variable speed electric motor, the hydraulic pump is placed axially adjacent to the stator and the rotor of the electric motor; therefore, the length of the hydraulic variable speed electric motor is great. In addition, the pressurized oil from the hydraulic pump is sent through the rotating hollow shaft and the integrated projecting shaft to the external case, and is sent from the external case to the hydraulic motor; therefore, the hydraulic variable speed electric motor similarly has the great length. Further, the hollow shaft and the integrated projecting shaft are supported by the bearings at three points, making the center shaft core difficult to access, and a large clearance between the external case and the rotating integrated projecting shaft is necessary. For this reason, there is a disadvantage of increased leakage of the pressurized oil from the clearance.